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Stellarium / stellarium

Stellarium is a free GPL software which renders realistic skies in real time with OpenGL. It is available for Linux/Unix, Windows and macOS. With Stellarium, you really see what you can see with your eyes, binoculars or a small telescope.
https://stellarium.org
GNU General Public License v2.0
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Backlit side of Saturn's rings #263

Open silcn opened 6 years ago

silcn commented 6 years ago

Just a feature request, sorry if someone's already suggested this. During crossings of Saturn's ring plane, there is usually a short period when Earth is on the opposite side of Saturn's rings from the Sun. When this happens, the backlit side of the rings is visible from Earth, and they appear much darker. This doesn't seem to be implemented in Stellarium yet (eg the rings should be darker in April 2025).

gzotti commented 6 years ago

Do you have any estimate or even measurement data or photos from previous occasions as reference for its darkening?

silcn commented 6 years ago

I'm not an expert on this; Focas and Dollfus (http://adsabs.harvard.edu/full/1969A%26A.....2..251F) estimated in 1969 that the brightness of the backlit side of the B ring is 1/50 of the brightness of the directly illuminated side. I couldn't find any more recent data or values for the other rings in a quick search, but at least this gives a rough idea. In fact the apparent brightness of the rings varies differently from that of the planet - for instance, the rings appear much brighter very close to opposition - and this doesn't seem to be implemented either. There are presumably some good models but I'm not the person to point you in the right direction.

gzotti commented 6 years ago

Thanks, that's a start. I think the ring brightness is just from ordinary Lambert reflection, there are no special effects. It might be possible to add some Oren-Nayar brightness push like for the Full Moon.

10110111 commented 1 year ago

Some information that might be useful: http://bjj.mmedia.is/data/s_rings/index.html

I think the ring brightness is just from ordinary Lambert reflection, there are no special effects.

Haha, no! At the very least, there's, like for lunar regolith, an opposition surge of brightness.

gzotti commented 1 year ago

This was a statement on the current state of implementation, with outlook on possible addition of an O-N effect. Feel free!